This invention relates to alarm devices. More specificaly it relates to patient disconnect alarms for ventilators.
Prior art patient disconnect alarms for ventilators merely monitored pressure in a ventilator circuit, eg., at the patient manifold, and if the pressure did not exceed a preset pressure limit an alarm would sound after a time delay.
This system has a serious drawback in that any restriction at the end of the patient circuit, eg., a tracheotomy tube, can cause circuit pressure to increase even with the patient disconnected, thus causing the monitor to falsely indicate that the patient is connected. If the pressure drop created by a bacterial filter and/or a humidifier is added to that of a tracheotomy tube it becomes relatively easy for a pressure monitor to falsely indicate that a patient is connected to the ventilator.
Also, if the pressure sensor is connected to the patient manifold, bacteria can enter the sensing tube, thus causing sterility and cross-contamination problems.